PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 515 



which are utilized in obtaiuing various salts of chrome. His 

 method is as follows : In a cast iron retort forming a continuation 

 of the bellows or blowing machine he introduces a certain quan- 

 tity of sulphur, which is lighted. This retort communicates with 

 the washer which conducts to the reducer containing chromate in 

 solution. On putting the belloAvs in motion the sulphurous acid 

 resulting from combustion is forced into the chromate solution 

 which is taken up while the nitrogen of the air used in the com- 

 bustion is disengaged. If bichromate of potash or of soda is 

 employed sulphates and sulphites of chrome, also of potash or of 

 soda are formed, which remain dissolved. If chromate of lime is 

 used the sulphate of lime is precipitated while the sulphate of 

 chrome remains in solution. Similar action takes place with the 

 chromates of lead and baryta. Separating the insoluble sulphates 

 by iilteration leaves tolerably pure sulphate of chrome. Mr. 

 Chaudet prefers to employ the bichromate of lime obtained direct 

 from the treatment of chrome ore b}^ lime. Chrome oxide (hy- 

 drated) may be produced by subjecting the chrome sulphate to 

 the action of ammonia or the alkaline carbonates. This oxide may 

 be used with advantage in coloring glass and porcelain. The sul- 

 phate and nitrate of chrome are used as mordants for silk and 

 wool in order to obtain novel shades with divers colorino- matters. 

 The acetate, nitrate, citrate and tartrate of chrome, easily obtained 

 by double decomposition, are used by Mr. Chaudet on cotton and 

 textrile vegetable productions. 



The use of the salts of chrome as a mordant with different tincto- 

 rial matters, will give the different colorations here recited : 



Campeachy produces blue and blue-black ; red wood, violet red; 

 Sanders, red; Jamaica rose-wood, golden yellow; quercitron, clear 

 yellow; fustic, mahogany yellow; woad, emerald yellow; curcu- 

 ma, copper yellow; Persian berries, straw color; roucou, flesh 

 color; madder, fallow red; nut gall, fallow brown; sumach, yel- 

 low brown; catechu, sienna clay; cochineal, purple red; carme- 

 line, carmine red; aniline, violet and fushia; yellow prussiate, 

 green; orchilla, violet red; red prussiate, green blue. 



By using the salts of chrome as mordants fast colors are obtained 

 which do not|turn green on exposure to the air, like, for example, 

 those produced by the use of the bichromate of potash. In the 

 latter jcase the oxygen is transmitted to the coloring matter, leav- 

 ing the oxide of chrome, which is naturally green. A different 

 result takes place when the oxide of chrome or a chrome base is 



